Carburetor fuel bowl inlet control



Feb. 13, 1968 I R. J. BRUNNER 3 CARBURETQR FUEL BOWL INLET CONTROL I Filed Oct. 21, 1965 m m i *jf yz/ ATTORNEY INVENTOR. vj (Qt/Para cffirzmner United States Patent 3,368,801 CARBURETOR FUEL BOWL INLET CONTROL Richard J. Brunner, Rochester, N'.Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Oct. 21, 1965, Ser. No. 499,514 1 Claim. (Cl. 261-70) ABSTRACT OF THE DISQLOSURE A manifold vacuum responsive piston positions carburetor metering rods for economy and power mixture ratios and positions a stop controlling movement of the fuel bowl float and the fuel bowl inlet valve. At high vacuums the stop permits unrestricted initial inlet valve opening and restricted further valve opening and prevents valve opening beyond a predetermined amount; at low vacuums the stop is positioned to permit unrestricted valve opening.

In starting an automotive engine after a hot soak period, in which the engine fuel system has been exposed to high temperatures, the fuel pump tends to deliver a mixture of hot fuel and fuel vapor at high pressure to the carburetor. When this mixture enters the carburetor and experiences the pressure drop between fuel pump pressure and the atmospheric pressure of the carburetor fuel bowl, it immediately expands. Upon such expansion, an emulsion of fuel and vapor is forced both through the internal vents of the carburetor into the mixture conduit and through the external vents into the atmosphere. Each is undesirable, because the fuel forcedinto the mixture conduit floods the engine causing a stall and because the fuel forced through the external vents increases the concentration of unburned hydrocarbons in the atmosphere.

This invention provides means to resist opening of the fuel bowl inlet valve by the high pressure of the hot fuel and vapor so that only the required amount of fuel is delivered to the fuel bowl. Thus flooding of the engine is avoided, and in addition, the amount of vapor emitted to the atmosphere is reduced.

The details as well as other objects and advantages of this invention are disclosed in the following description and in the drawings in which:

FIGURE 1 is a side elevational view of acarburetor shown partially in section to illustrate this invention;

FIGURE 2 is an enlarged view taken generally along line 22 of FIGURE 1 illustrating the bracket and modulated stop which limit opening of the fuel bowl inlet valve; and

FIGURE 3 is a further enlarged sectional view along line 33 of FIGURE 2 illustrating the details of the modulated stop.

Referring first to FIGURE 1, fuel is delivered to the carburetor 10 through a fuel inlet passage 12 opening into a fuel bowl 14 past an inlet valve 16. A float 18 is supported on an arm 20 pivoted on a pin 22 to control the opening movement of valve 16. As the fuel level in bowl 14 drops, float 18 and arm 20 pivot in a clockwise direction about pin 22 to permit the inlet valve 16 to open and allow fuel flow through inlet passage 12.

A fuel delivery passage 24 extends from fuel 'bowl 14 to a venturi 26 disposed in a mixture conduit 28. A throttle 30 controls flow through mixture conduit 28.

A piston 32 is subjected through a passage 34 to the vacuum in mixture conduit 28 downstream of throttle 3,368,801 Patented Feb. 13, 1968 30, Piston 32 positions a metering rod 36 within a metering orifice 38 so that during low manifold vacuum, metering rod 36 is withdrawn from orifice 38 to permit an enriched mixture for power operation of the engine.

A bracket 40 having an extension 41 is secured to piston 32 and overlies float arm 20. A modulated stop 42 is mounted on bracket extension 41 and contacts float arm 20. As shown in greater detail in FIGURE 3, modulated stop 42 includes an adjustable support 44 and a contact member 46 biased by a spring 48.

When the throttle is closed or nearly closed and'the engine speed is low, piston 32 is pulled downwardly by the vacuum in mixture conduit 28 to position modulated stop 42 closely adjacent float arm 20. A small clearance is left so that fioat arm 20 may allow inlet valve 16 to open an initial amount sufficient to supply the fuel required for low speed operation.

If the carburetor has been subjected to an extended hot soak so that a substantial amount of fuel has evaporated from the fuel bowl, the float will attempt to drop further to allow the inlet valve to replace the evaporated fuel. Such secondary movement of the inlet valve 16 is resisted by the spring 48 so that a modulated secondary opening movement of the inlet valve 16 is permitted. Thus the fuel flow through inlet 12 is restricted so that a substantial amount of fuel is not immediately vaporized as it enters the fuel bowl.

When the throttle 30 is opened and the engine demand for fuel is greater, piston 32 is raised and positions modulated stop 42 to permit unrestricted opening movement of inlet valve 16. Thus this control prevents undue vaporization of fuel in a carburetor without interfering with engine operation.

I claim:

1. An internal combustion engine carburetor comprising a mixture conduit, a throttle disposed in said mixture conduit, a fuel bowl, a fuel passage extending from said bowl to said mixture conduit, said fuel bowl having an inlet, a valve controlling flow through said inlet, a float responsive to the fuel level in said bowl, a pivoted arm extending from said float to said valve to position said valve .in accordance with the fuel level in said bowl, said float and arm permitting said valve to open as the fuel level decreases, a piston responsive to the pressure in said mixture conduit downstream of said throttle, a bracket secured to said piston and having an extension adjacent said arm, and a modulated stop including an adjustable support mounted on said bracket extension and a spring biased contact member supported thereby for contact with said arm, said piston positioning said bracket and stop at relatively low pressures in said mixture conduit whereby said contact member will permit unrestricted initial valve opening and restricted further valve opening and will prevent valve movement beyond a predetermined opening, said piston positioning said bracket and stop at relatively high pressures in said mixture conduit whereby said contact member will permit unrestricted valve opening.

References Cited UNITED STATES PATENTS 2,873,957 2/1959 Lunn 261-72 X 3,052,453 9/1962 Carlson 26l72 3,256,870 6/ 1966 Walker.

RONALD R. WEAVER, Primary Examiner.

HARRY B. THORNTON, Examiner. 

